/**
*      author: Y_Yao
*      created: 2025-03-19 17:53:08
**/

#include<bits/stdc++.h>

#define int LL
using namespace std;
using LL = long long;
const LL LLINF = 9e18;
const int INF = 0x3f3f3f3f;
const int N = 2e3 + 7;
int n;
int ans;

void solve()
{
    cin >> n;
    vector<int> d(n + 1);
    for(int i = 1;i <= n;i++)
    {
        cin >> d[i];
    }
    sort(d.begin(),d.end());
    for(int i = 1;i <= n;i++)
    {
        for(int j = i + 1;j <= n;j++)
        {
            auto it = lower_bound(d.begin() + 1,d.end(),d[i] + d[j]) - d.begin();
            ans += it - j - 1;
        }
    }
    cout << ans << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}